Why would that be true in any alternate versions of these contests? I understand the enormous incentive mechanisms involved, and yet I cannot see this being obviously true.

Edit to add: if the authorship of the submitters is as above reproach as we are led to assume, why can that not be the case for the NIST decision panel itself?

Edit 2: answered already elsewhere: https://news.ycombinator.com/item?id=31993896